The present invention relates to contactless integrated circuit readers and data transmission by inductive coupling.
As represented schematically in FIG. 1, a contactless integrated circuit reader 10 operating by inductive coupling is an active system that sends an alternating magnetic field FLD by means of an antenna circuit 11 and that sends data by modulating the amplitude of the magnetic field sent. Conversely, a contactless integrated circuit 20 is a passive device that does not send a magnetic field and comprises an antenna circuit 21 comparable by analogy to the secondary winding of a transformer the primary winding of which would be constituted by the antenna circuit 11 of the reader. The magnetic field FLD sent by the reader causes an induced alternating voltage Vac to appear in the antenna circuit of the integrated circuit, said induced voltage copying the amplitude modulations of the magnetic field and enabling the integrated circuit 10 to receive the data sent by the reader, after filtering and demodulating the induced voltage Vac. Furthermore, a contactless integrated circuit 20 sends data to such a reader by load modulation, i.e. by short-circuiting its antenna circuit by means of a switch driven by a load modulation signal Sx. The antenna short-circuits cause a disturbance of the magnetic field FLD that is passed onto the antenna circuit of the reader 10. The latter can therefore extract the load modulation signal Sx by filtering the signal present in its antenna circuit 11 and deduce the data sent by the contactless integrated circuit from it.
With reference for example to the ISO standards 14443-2/A or 14443-2/B or ISO 1569, designated hereafter “ISO/A”, “ISO/B” and “ISO15”, the antenna circuit of a contactless reader is excited by an alternating signal of a frequency of 13.56 MHz, the data transmission to a contactless integrated circuit is carried out by modulating the amplitude of the magnetic field with a modulating trough of 100% (ISO/A), of 10% (ISO/B) or of 10% to 30% (ISO15). The data transmission to a reader is carried out by load modulation by means of a sub-carrier of 847 KHz that is Manchester coded (standard ISO/A) or biphase shit keying (BPSK) coded (standard ISO/B) or by means of a sub-carrier of 423 KHz that is Manchester or frequency shift keying (FSK) coded (IS015).
The applications of this data transmission technique by inductive coupling are currently increasing, particularly in the fields of electronic payment and access control (smart cards and electronic badges) and in product identification (electronic tags). The contactless integrated circuits are arranged on portable supports (plastic cards, tag supports) having an antenna coil integrated therein. The antenna coil is sometimes integrated directly into the silicon wafer of the integrated circuits (“coil on chip”), in so-called “proximity” applications in which the maximum distance of communication is short and on the order of a few millimetres.
In many applications, the contactless integrated circuit readers are in the form of fixed terminals. However, these contactless terminals are capable of recording different pieces of information relating to the operations carried out, which are sometimes necessary to collect to correctly manage the installations. Thus, an access control terminal is capable of recording each time the door opens, the date, the time and the identity of the badge with which the opening of the door was requested. Similarly, an automatic payment terminal is capable of recording the time of each transaction and the identity of the card with which payment was made. In the applications that involve several terminals, it is sometimes desirable for this information to be collected by a data centralization system. To collect the information recorded, it is therefore necessary to provide an infrastructure of electric cables enabling the centralization system to be connected to each of the terminals. In other applications, the reading of the data recorded by a terminal is done manually by means of a terminal reader comprising a connector that is inserted into an output port of the terminal.
These various operations of reading data in fixed terminals prove to be tedious when they are done manually or costly when they require an infrastructure of electric cables.
The present invention aims to overcome this disadvantage.